This invention relates to a process for chlorodenitrating aromatic compounds. In particular, it relates to chlorodenitrating aromatic compounds using less chlorinating agent and lower temperatures, then recycling the product mixture to increase the yield.
U.S. Pat. Nos. 4,470,930 and 4,582,948 describe a process for the nuclear chlorination of aromatic compounds. In that process, an aromatic compound having nitro and other groups on the ring is heated in the presence of a chlorinating agent, which results in the replacement of the nitro groups by chlorine. To obtain a high yield, excess chlorine and higher temperatures are used.
While the yield in the process described in those patents is good, the product also contains partially chlorinated intermediates, unreacted starting material, and overchlorinated byproducts. Separation of the desired product from these undesirable byproducts and unreacted starting material by distillation can result in the decomposition of the partially chlorinated intermediates and the unreacted starting material.